Pouch ileitis is the most poorly understood complication of ileal reservoir surgery. Variability in definition of this syndrome may account for differences in incidence rate, associated symptoms, and response rate to therapy present in the literature. Outcomes of 19 episodes of pouch ileitis in patients having undergone prior colectomy and continent ileostomy construction for presumed ulcerative colitis were analyzed. An episode of pouch ileitis was characterized by: (1) abdominal pain, (2) increased ileal output, (3) mucosal inflammation within the continent ileostomy, and (4) absence of other recognized concurrent postoperative complications. The mean time of occurrence after construction of the continent ileostomy was 25 months (range 3-54 months). The mean length of follow-up of patients included in this analysis was 49 months from the time of continent ileostomy construction (range 22-101 months). Associated clinical symptoms included bloody effluent (53%), nausea or emesis (47%), and fever (42%). Endoscopic features were often nonspecific, with mucosal erythema (84%), edema (79%), friability (58%), and mucosal ulceration (53%) the most common. In those episodes of pouch ileitis where ileoscopy revealed no evidence of mucosal ulceration, complete resolution of the episode occurred 89% of the time, with 78% treated with antibiotics alone. In those episodes where mucosal ulceration was described on ileoscopy, 40% of episodes completely resolved after medical treatment, 20% with antibiotics alone. The varied clinical symptoms, endoscopic findings, and response to treatment raises the possibility that what has previously been described in the literature as pouch ileitis may be a heterogeneous group not of single etiology.(ABSTRACT TRUNCATED AT 250 WORDS)